On April 11, 1970, three astronauts entered the Apollo 13 spacecraft on top of the Saturn V rocket to prepare for the third U.S. manned mission to the moon. The number 13 is not too auspicious in the West, but considering that Apollo 11 and 12 have successfully landed on the moon, people think that there should be no problem this time.
It has been pointed out that Apollo 13 was launched at 13:13 Houston time and would enter the lunar gravitational range on April 13, so it is even more unlucky. But the spacecraft was launched at the Kennedy Space Center, where it was at 14:13.
Apollo 13 was launched
Apollo 13 was commanded by Jim Lowell, with the command module and lunar module pilots Jack Swegert and Fred Hayes respectively. At 14:13 EST, the giant rocket Saturn V, with a total height of more than 110 meters, ignited, and the rocket emitted a huge roar, spewing out long flames, sending Apollo 13 into the sky. The Reliability of saturn V was excellent, and none of the launches failed, but this time there was a little problem:
The second stage of the rocket had 5 J-2 engines, and the one in the center was shut down early, so it had to extend the combustion time of the other 4 engines. A J-2 engine of the third stage also extended the operating time, and finally succeeded in delivering Apollo 13 accurately to the berthing orbit around the earth. After another 1 and a half laps in the berthing orbit, the third stage engine was activated again, and the spacecraft officially flew to the moon.
The Apollo spacecraft used a three-cabin structure, with the lunar module at the time of launch at the bottom, followed by the service module and the command module. After entering the Earth-Moon transfer orbit, the command/service module should be separated from the lunar module, turn around and then re-dock to form the correct combination. In the dozens of hours that followed, which could be described as "boring," everything seemed to be going well, the spacecraft had already traveled more than 320,000 kilometers from Earth, and it was planned that they would land on the Flata-Mauro Heights on the lunar surface.
The three-cabin structure of the Apollo spacecraft
What ground controllers and astronauts don't know, however, is that there is a "time bomb" on the spacecraft that is about to develop into a fatal accident: the command/service module uses 3 large hydrogen fuel cells to power the equipment, and the required hydrogen and oxygen are stored in liquid hydrogen tanks and liquid oxygen tanks respectively. There are two liquid oxygen tanks in the service cabin, each containing 148 kilograms of liquid oxygen, and the "time bomb" is the No. 2 liquid oxygen tank.
A drill was conducted prior to the launch of the Saturn V, and after the drill was completed, the crew needed to empty the No. 2 liquid oxygen tank, and they used the heating method to turn on the heater in the liquid oxygen tank with a voltage of 65V. However, the circuit in the liquid oxygen tank was originally designed to be 28V. After the heating began, the temperature control switch in the tank was burned and melted, and during the 8-hour heating process, the temperature inside the tank exceeded 500 ° C at one point. The insulation of the wire is burned out and damaged.
However, no one knew about this situation at the time. After the launch, the astronauts turned on the agitation fan of the No. 2 liquid oxygen tank several times to ensure that the liquid oxygen was evenly distributed. Except for the first time, when the liquid oxygen reserves were incorrectly displayed, the second and third times were normal. At 55 hours, 53 minutes and 58 seconds after launch, the ground controller asked to turn on the agitation fan again, and after 22 seconds, the fan was activated.
Command/service module for Apollo spacecraft
This operation caused disaster, due to the broken insulation, an electric spark appeared between the fan and the heating device in the tank, and in the oxygen environment, the insulation was ignited, causing an explosion. After a deafening explosion, a low-voltage alarm appeared on the B-line power bus, and Swegt reported to the ground: "We're in trouble." After being questioned by ground personnel, Commander Lowell reconfirmed: "We are in trouble!" ”
This time it was indeed troublesome: the explosion of the No. 2 liquid oxygen tank not only blew itself up, but also destroyed the No. 1 liquid oxygen tank not far from it, and two of the 3 fuel cells were damaged. The astronauts in the command module didn't know what was going on until thirteen minutes after the explosion, when Lowell looked out the porthole and saw a terrifying scene:
"We're in trouble!" (Movie Scene)
"We're leaking something into space!" There is no doubt that these things are oxygen. Ground personnel also detected anomalies in the service module through telescopes. The impact of the explosion also derailed the ship from course. At first, the astronauts were just frustrated: the mission to the moon was likely to fail. But soon, they discovered that it wasn't the moon landing that they had to worry about, but their own lives: now it was unknown whether they would even be able to return to Earth alive!
The oxygen in the liquid oxygen tank is not only used for fuel cell power generation, but also for the breathing of astronauts, and the usual drinking water also comes from the water formed after power generation, and it also needs to use electricity to keep warm. Now the No. 2 liquid oxygen tank is basically empty, the oxygen in the No. 1 liquid oxygen tank is also rapidly draining, the voltage of the only remaining fuel cell is also decreasing, and the battery equipped with the command chamber will be exhausted. If the astronauts continue to stay in the command module, they will face the situation of no oxygen, no water and no electricity, which is a dead end.
The most critical thing is that the main engine of the spacecraft is installed in the service module, and electricity is also required to start the main engine. Now that the service module has been blown to smithereens, it is almost impossible to use the main engine to change orbit and return to Earth. At this time, the ground control center and the astronauts thought of a life-saving straw: the lunar module.
Lunar module (left) and damaged service module (right)
The lunar module has a 2181 ampere battery, which can meet the needs of a 45-hour lunar mission, and also carries oxygen, which can be calculated to supply 3 astronauts with 90 hours of breathing. For the purpose of lunar landing and return, the lunar module is also equipped with a descending engine and an upper upgrade engine, which can be used for the spacecraft to change orbits.
There was no other choice, and at 58 hours and 40 minutes, the lunar module was activated and the command/service module was closed. However, the command module cannot be abandoned at this time, because only the command module can re-enter the atmosphere and return to the ground. At this time, all three astronauts have entered the lunar module, and 5 hours after the explosion, the engine of the descending section of the lunar module has performed its first work, lasting 34.23 seconds, transferring the spacecraft from the lunar approach orbit to the Earth-Moon free-return orbit.
The Earth-Moon Free Return Orbit is a figure-8 orbit that bypasses the far side of the Moon, which cleverly utilizes the Moon's gravitational pull and can return to Earth without additional propulsion, with only minor corrections halfway through. As a result, the fate of astronauts seems to have changed: they will not be abandoned in the cold and lonely outer space, but will regain hope of returning to Earth.
The Earth and Moon are free to return to orbit
But so far it is only hope, although the lunar module can provide the thrust to go home, but the three astronauts need to stay in it for more than 80 hours, such a long time to breathe, drink water, but also not to freeze to death, these things that are easy to satisfy on the earth, in the Apollo 13 hundreds of thousands of kilometers away from the earth, have become a life and death problem.
Although the oxygen in the lunar module is sufficient, people will continue to excrete carbon dioxide when breathing, and if the concentration of carbon dioxide is too high, it will cause poisoning, coma and even death. Lithium hydroxide filters were used to remove carbon dioxide, and the filters in the lunar module were not enough, so the astronauts took the filters in the command module.
At this point they were surprised to find that the specifications of the two types of filters were different! The lunar module was developed by Grumman, the filter tank and the corresponding mounting opening are round, while the command module was designed by North American Airlines and equipped with a square filter, which has the problem of "donkey lips not for horse mouth".
Two sizes of the filter
With the passage of time, the concentration of dioxide in the lunar module continues to rise, and the situation is critical. Ground personnel experimented with socks, tape and other things that could be thought of, and finally came up with a solution:
Cover the back of the square filter with cardboard and make an arch to allow the gas to circulate, then put on a plastic bag, open an opening and tape to the exhalation hose of the spacesuit, and tape the other end of the hose to the circular filter entrance of the lunar module. Such a set of handmade "complex" emergency equipment actually solves the problem of high carbon dioxide concentration, and the effect is good!
Cardboard and tape solved the problem
The problem of breathing is solved, but the problem of drinking water is not so easy. Unable to produce water through fuel cells, astronauts had only a measly poor 12.8 kilograms of water reserves when they entered the lunar module. Some of this water is also used to cool electronic devices, so there is less water to drink.
In order to conserve water, but also to save electricity, the non-essential electrical appliances of the lunar module were turned off, including the insulation system. Energy consumption is reduced to one-fifth of the original, and cooling water consumption is reduced. In order to save water, the astronauts also tried their best to diet, and the daily food intake dropped to one-fifth of the normal level, and finally everyone was seriously dehydrated, and one person lost more than 14 kilograms of weight.
Astronauts aboard Apollo 13
Without the insulation system, the temperature in the cabin dropped to 3.3 degrees, and the astronauts were frozen and shivering, and it was not easy to last for a few days. But the saved electricity was able to recharge the command module batteries, which was key to their ability to re-enter the atmosphere and return to the ground. Eventually, when the lunar module was abandoned, only 20% of the electricity remained.
All of these difficulties can be overcome, but if the next operation is not successful, the spacecraft will miss the Earth or burn in the atmosphere. After the spacecraft bypassed the far side of the moon, it needed to be ignited in the correct direction for about 4 and a half minutes to correct the course, but how to find this direction became a problem.
Under normal circumstances, navigation uses starlight, that is, to find a navigation star, and according to its orientation, you can calibrate the direction of the spacecraft. But the service module after the explosion released a large amount of debris flying around the spacecraft, and the sunlight reflected by them made it impossible for navigation telescopes to point at real stars.
The damaged service cabin produced a lot of debris
NASA came up with a simple and crude method: point the navigation telescope at the sun, although the sun is large in diameter, it will produce a certain error, but it will not be disturbed by debris. Lowell made a manual calculation according to the direction of the sun, completed the navigation, and after the engine ignited for 263.82 seconds, the heading correction effect was basically achieved, but there was still a certain speed error.
To compensate for these errors, the Apollo 13 later made two more corrections, and the engine ignited for 14 seconds and 21.5 seconds, respectively. Some sources say that because the computer was turned off in order to save electricity, the timing was done with a watch worn by astronauts. Regardless of the veracity of the claim, the effect of these two corrections is very good.
With about 2 hours and 40 minutes left before entering the atmosphere, the service module was finally abandoned. For the first time, the astronauts had the opportunity to see the condition of the service module: a large panel was completely blown up, and the inside was devastated and badly damaged.
Devastated service cabin
1 hour and 10 minutes before re-entering the atmosphere, the "Noah's Ark", which accompanied the astronauts for several days, separated from the instruction module. The astronauts had entered the command module to prepare for landing, and the lunar module was useless at this point. It has made great contributions to this mission and believes that it has a special position in the minds of astronauts.
After 142 hours, 40 minutes and 45 seconds after launch, four days after the explosion, Apollo 13, which had been in space for a total of 6 days, finally returned to the atmosphere, returned at a speed of about 11 kilometers per second, and after experiencing a thrilling thermal barrier, splashed in the Pacific Ocean at 18:07 GMT on April 17, only 1 nautical mile away from the intended location, and the astronauts were subsequently rescued by the aircraft carrier Iwo Jima.
The Apollo 13 command module splashed down on the Pacific Ocean
Apollo 13 has been called "a successful failure" and is an important player in the history of manned spaceflight. After learning of his distress, the world paid close attention to it. The cause and handling process of this incident have a good reference significance for future lunar spacecraft and other manned space missions, and have had a far-reaching impact. Under such a dangerous situation, the 3 astronauts did not mess up the danger, completed various key operations brilliantly, and finally successfully saved themselves. Their strong psychological qualities are also really admirable.
Three astronauts who survived
So the question arises: there are many people who question whether the entire Apollo moon landing program is fake, and give many reasons, but can the Apollo 13 incident be faked? Or is it necessary to make this fake?